The present invention relates generally to methods and systems used in the purification and decontamination of water, sludge, and other liquids which contain toxic or undesirable chemicals and pathogens. More particularly, the system of the present invention pertains to liquid decontamination systems whereby the destruction and/or elimination of contaminants is initiated by an electrical discharge within a liquid stream.
A significant amount of research and development has been undertaken in recent years towards environmental clean-up operations, and in particular to the purification and decontamination of ground water, waste water, and drinking water. The need for decontamination of water can vary from the continuous treatment of industrial waste water to dealing with one-time contamination of water pools or ponds at a single location. Accordingly, methods are needed which are feasible on both a large and small scale.
A variety of techniques have been used in the prior art to destroy or remove contaminating and toxic materials in water supplies. These include the use of shock waves created by ultrasonic vibrations and exposing the water to ultraviolet radiation. Electricity has also been employed as a decontamination agent, such as by introducing positively charged ions into a water stream to cause coagulation and separation of particles, and by the passing of electric current within a fluid chamber whereby the current flow between the anode and cathode has a toxic effect on microorganisms nearby.
Chlorination is well known and effective in limiting bacteria and microorganisms but has little effect on organic chemicals. Conversely, activated carbon filters can remove organic chemicals but such filters are extremely costly and require regular maintenance.
The use of ozone (O.sub.3) injection can also be effective. However, to be efficient, an ozonation facility must be extremely large. Therefore, its cost and size renders it unsuitable for use, for example, to clean up small contaminated ground water and waste water sites. Hydrogen peroxide injection systems have also been used, some with UV flash lamp activation, to create the --OH radicals necessary to combine with the organic compounds. This technique provides adequate cleanup of contaminates and organic chemicals but is costly because of the large requirement for high purity hydrogen peroxide and the need for regular maintenance due to the surface contamination of the UV flash lamps which prevents proper exposure of the hydrogen peroxide to the UV energy.
Activated carbon filters do an adequate cleanup job for organic chemicals but are extremely costly and must be changed regularly and thus do not promise to solve the problems on a national basis.
In a related problem, thousands of manufacturing industries nationwide must contend with a by-product, or side effect of production, that may be dangerous to the general public or the local environment. The production process itself may create organic chemicals or other contaminants that are harmful to the environment, and to humans. In the food industry, the problem is more frequently due to the fact that many food provisions attract, or take on, bacteria and/or biological organisms that are harmful if consumed. These pathogens (salmonella, virus, bacteria, etc.) pose a challenge for the manufacturer at some point in the production process, and before shipment to retail outlets. In most cases, the manufacturer will use a chemical disinfectant or utilize a process at the plant which will virtually eliminate the possibility of problems due to product contamination. This is good for the end consumers, but poses another problem for the environment if these disinfectants or chemicals are discharged from the plant into nearby bodies of water or landfills, which may leech into ground water systems.
There are many types of disinfectants and chemicals used in this type of processing. One of the most effective is phenol-based disinfectant. Phenol combats pathogens, and other harmful compounds, and is used widely by many various industries. The side effect to use of a phenol-based disinfectant is that it poses a threat to the environment because of its high Biological Oxygen Demand (BOD). This BOD competes for oxygen with other higher chain organisms when released into the environment. The Environmental Protection Agency (EPA) currently enforces a limit of 0.5 ppm daily average and 1.0 ppm maximum limit if discharging into the local environment. This concentration of phenol in the native environment apparently poses no threat to the natural food chain, and therefore is acceptable by government standards. However, many industries are either non-compliant with this regulation, or have no cost-effective alternatives for destroying the disinfectant before it is released into the environment. Therefore, many industries are installing in-house waste water treatment technology to keep their product safe for end users and for the local environment.
In the production of poultry breed stock, products, and eggs, many process farms and plants utilize phenol as a disinfectant. Some are enforcing a salmonella-free process which is unique to the entire industry. This process protects their employees and end consumers from possible salmonella contamination. Part of the process requires the use of phenol as a disinfectant for washing down equipment, machines, and the general facility. The wash down run-off water with the phenol by-product is often collected and discharged locally into a small body of water. This poses a problem because the concentration of phenol is typically beyond the allowable limits as set by the EPA for local discharge. A wash down volume of 8,700 gal/week with phenol concentration of 20 PPM or more is not unusual.
Another problem exists for the thousands of waste water processing plants in the USA which utilize some form of sludge de-watering equipment. The bulk of the waste treatment plants in the United States use biological processing or living organisms called "bugs" as a means of final processing of the waste water from the sewer systems or industrial processes. The end result is that the only solid matter remaining after the waste material processing are the "bugs" themselves. The water containing these bugs in the final processing tank is called sludge. The problem created by this means of waste processing is the fact that the remaining solid material must be removed and disposed of before the processed water can be recycled or expelled to a river or stream.
The limit to operating capacity is the de-watering rate. The cell structure of the organisms which comprise the sludge holds water and significant energy and time is required to remove this water. In many cases conventional treatment equipment can not remove a sufficient amount of water to allow the transfer of the processed sludge cake to a landfill without further drying. If the wet sludge is sent to a landfill rated for wet sludge type waste material then the disposal costs are much higher.
Many types of de-watering equipment exist to physically separate the solid material from the sludge. Examples include the belt press, the plate and frame press, and the centrifuge. Once the solid material is removed by this de-watering equipment, it must be disposed of in some manner. The primary approach is the transportation of this material to a land fill. The limitations to this approach are the time and energy required to physically remove the water and the dryness of the compressed material or "cake" after the de-watering process. If the de-watering step is too slow, then extra equipment must be employed to process a certain flow rate of sludge. If the cake is not dry enough, the material must be further processed or disposed of in a special landfill which costs much more to utilize. If a landfill can be found to accept the wetter cake, then there is a significant increase in cost associated with transportation of the heavier material due to the additional water that was not removed. The net result is, if the de-watering rate could be doubled, a given volume of sludge could be processed in half the time with half as much de-watering equipment. If the cake could be dryer, then all the solid material could be disposed of at minimum cost. Such a process would save significant amounts of capital equipment and operating costs.
What is needed, then, is a liquid purification and decontamination system which can effectively destroy or remove a variety of organic materials and chemical toxins at relatively low cost, which does not require the addition of other chemicals or further processing of the contaminated water, and which can be adapted for use in both large and small scale operations. What is also needed is sludge treatment process which can solve both the de watering rate problem and the dryness of the cake problem with a single operation. Such a system is presently lacking in the prior art.